Ink repellent inking pad and cover for stencil printing devices



Jan. 4, 1966 J. J. REICH 3,

INK REPELLENT INKING PAD AND COVER FOR STENCIL PRINTING DEVICES FiledNov. 19, 1962 gg M LL;

v- 4 gig/5 United States Patent 3,227,073 INK REPELLENT INKING PAD ANDC(WER FtER STENCTL PRENTENG DEVlCES John 3. Reich, 6314 W. PattersonAve, Chicago, Ill. Filed Nov. 19, 1962, Ser. No. 238,669 9 Claims. (Cl.191-125) This invention relates to an ink distributing pad and covertherefor and more particularly to an ink distributing cloth and coverfor use in duplicating apparatus. This application is acontinuation-in-part of Serial No. 817,973, filed June 4, 1959, and nowabandoned.

Most conventional duplicating apparatus, whether of the hand stamp type,belt type or rotary drum type employ a cloth member to distribute theprinting ink onto the surface of a stencil or similar printing matrix.The ink distributing cloth is generally referred to as an inking pad andwill be designated as such herein for purposes of explanation.

In conventional rotary duplicating apparatus, i.e., stencil duplicators,the inking pad, which is generally constructed from commerciallyavailable cloth such as cotton flannel, wool, rayon, etc. or laminationsof these materials, is physically attached to the surface of aperforated drum or cylinder which serves as an ink reservoir. Ink issupplied to the interior of the perforated drum, and centrifugal forceduring the operation causes the ink to pass outwardly through theperforations in the drum and into the pores or interstitial passages inthe inking pad. The ink is drawn through the pad and forced through theopenings in the stencil by a pumping action created by the alternatingpressure developed by contact with the roller of the duplicatingmachine. Thus, the ink passes through the stencil onto the paper to beprinted which is pressed against the surface of the stencil by theimpression roller. The inking pad acts to hold the ink within therotating perforated drum and also, under pressure from within thecylinder, to evenly distribute ink over the surface of the stencil. Theink employed can either be in a fluid state or can be paste, whicheveris desired. In all instances, however, an inking pad is essential to theefficient performance of the duplicating apparatus.

The presently available inking pads have several inherent limitationswhich necessitate their frequent removal from the duplicating apparatusand which cause difliculties which have not been heretofore adequatelycompensated for. Some of the limitations present in conventional inkingpads for duplicating apparatus are: (1) the ink vehicle tends toseparate from the ink pigments in the inking pad due to capillary actionwithin the inking pad; (2) the ink vehicle which becomes separated fromthe ink pigment accumulates on the lower surface of the cylinder anddrips off the cylinder; (3) the separated ink vehicle evaporates fromthe inking pad causing the pad to become dried out; (4) the ink vehicleis preferentially absorbed from the ink pigment by the inking padcausing a stiff crust of pigment to be built up within the perforatedcylinder; and (S) the separation and evaporation of the ink vehiclecauses inks to lose their characteristics upon prolonged storage withinthe duplicating apparatus.

All of the above enumerated difliculties, and others, stem from theseparation of the ink vehicle from the ink pigments due to capillaryaction within the inking pad. Several modifications have been devised tocounteract the effect of the ink vehicle separation by capillary actionincluding; the use of high viscosity oil based inks, the use of waterbased inks conventionally containing dyes, the use of emulsion inks,frequent changing of the hiking;

pad and regular cleaning of the perforated cylinder to re- 3,227,073Patented Jan. 4, 1966 move caked ink. The remedies presently availableto users of duplicating apparatus do not solve the problems attendantwith the use of inking pads, in which the capillary separation of theink vehicle takes place, and maintenance costs and higher cost inksgreatly increase the cost of operation of the duplicating apparatus.

The conventional inking pad cover, which is placed on the surface of theinking pad when the duplicating apparatus is not in service, is subjectto the same disadvantages as is the inking pad. Two forms of duplicatorcovers are presently available, the absorbent cover and the barriercover. The barrier cover, which is generally a heavy wax or plasticcoated paper sheet, is constructed in a manner to prevent theevaporation of the ink from the surface of the inking pad. However, thenature of the barrier cover is such that it is completely nonporous andthe barrier cover will not absorb any ink. If excess ink or separatedink vehicle is present upon the surface of the inking pad it will runbetween the inking pad and cover to the lower surface of the cylinderwhere it will drip onto the floor or supporting means for theduplicating apparatus. The absorbent cover, generally constructed of akraft or sulphite paper, is made to absorb excess ink on the surface ofthe inking pad. The absorbent cover is, therefore, also subject to thecapillary separation of the ink vehicle from the ink pigments, and doesnot prevent the drying out of the inking pad and the formation ofpigment crusts within the inking pad and perforated cylinder.

It is the principal object of this invention to provide an inking padand/ or cover which diminishes the capillary separation of the inkvehicle from the ink pigments.

It is another object to provide an inking pad and/0r cover for use induplicating apparatus which eliminates the necessity for frequentcleaning of the duplicating apparatus and replacement of the inking padand cover. A further object is to provide an inking pad and/or coverwhich reduces the evaporation of the ink vehicle and reduces thecrusting of the ink upon the surface of the inking pad and perforatedcylinder. A still further object of the invention is to provide aninking pad and/or cover for use in duplicating apparatus whichdiminishes the capillary separation of the inking vehicle from the inkpigments which is economical to construct and which is convenient to usein duplicating apparatus.

These and other objects of the invention will be perceived from thefollowing detailed description and from the drawing in which:

FIGURE 1 is a perspective view of an ink reservoir for a duplicatingapparatus showing a specific embodiment of the inking pad and cover.

In general, the inking pad 6 and cover 8 shown in the drawing are of aweb material which is constructed from fibers which are ink repellent,or have an ink repellent coating applied thereto. The ink repellentcoating is applied to the inking pad 6 and cover 8 in an amountsufficient to reduce or prevent the capillary flow of ink vehicle withinthe inking pad 6 and cover 8 but less than that which blocks theinterstitial passages and prevents ink from pasing therethrough underpressure from an ink reservoir and under printing pressure.

For purposes of explanation the inking pad 6 and cover 8 are describedhereinafter as employed with a conventional duplicating apparatus of therotary drum type. As shown in the drawing, the conventional rotaryduplicating apparatus includes a perforated drum 10 which contains aplurality of perforations l2 evenly spaced over its surface. Ink issupplied to the interior of drum it) by conventional means (not shown).

The inking pad 6 is provided with suitable means 14 for attaching thepad to the drum It) and securing the same tightly against the outersurface of the drum 10.

The inking pad 6 is composed of a porous web material or a plurality oflayers of porous web material which is constructed from ink repellentfibers. For oil base inks, repellent fibers, such as fluorocarbon resinfibers (e.g., polyfluoroolefin fibers) are employed. For Water baseinks, fluorocarbon fibers are employed as well as polyolefin resinfibers such as polypropylene. A sponge material is also contemplated aswithin the use of the term fiber. The inking pad 6 may also be composedof a nonrepellent material such as cotton flannel, silk, Wool, rayon ornylon, etc., which are treated with an ink repellent coating compound toform an ink repellent coating on the surfaces of the individual fibersthat make up the pad. Suitable ink repellent coating compounds are thechromium complexes of perfluoroacids, fluorocarbon resins, siliconeresins, waxes, the insoluble salts of fatty acids having at leastapproximately 12 carbon atoms and chromium complexes of fatty acidshaving at least approximately 12 carbon atoms. It should be noted thatthe use of the term coating is intended to encompass both the formationof a coating on the surface of the fiber, such as occurs when usingsilicone resins or the salts of fatty acids, and the chemical reactionwith the inking pad fibers such as occurs when using the chromiumcomplexes of ctatty acids or perfluoroacids.

When the ink repellent coating is applied to the fibers of thenonrepellent material, care must be taken to avoid applying the coatingcompounds in an amount which blocks interstitial passages of thematerial. If too much coating compound is applied, the centrifugal forceand the pumping action will be insufficient to cause the ink to passthrough the pores in the ink pad material. It has been found that inmost instances a coating which is from about 0.1 to percent by weight ofthe ink pad material is sufiicient to provide the material with an inkrepellent coating which resists and diminishes the ca pillary separationof the ink vehicle and ink pigment. When more than 25 percent by weightof ink repellent coating is employed, the inking pad normally has aportion of its interstitial passages blocked and the fiow of printingink therethrough is hindered to such an extent that poor copies areobtained from the duplicating apparatus. By employing a pad constructedas described above, the ink employed with the pad may be of an improvedcomposition. In this connection, the ink need not be made to withstandcapillary separation. Therefore, the ink more readily dries on the paperthan the ink employed with previously available inking pads.

In the illustrated embodiment, the cover 8, which is shown disposedabout the surface of the inking pad 6 is composed of a porous webmaterial constructed from ink repellent fibers. For oil base inks,repellent fibers such as fluorocarbon resin fibers (e.g.polyfluoroolefin fibers) are employed. For water base inks, fluorocarbonfibers are employed as well as polyolefin resin fibers, such aspolypropylene fibers. The porous web material may also be constructedfrom nonrepellent fibers such as sulphite paper, kraft paper, cottonflannel, silk, wool, rayon, nylon cloth, etc. which are coated with anink repellent coating compound, such as that described above inconnection with the inking pad that renders the cover repellent to theink and reduces the capillary separation of the ink vehicle and inkpigment. The amount of coating compound applied to the material islimited to a value such that the cover remains porous, thereby allowingany excess ink present on the surface of the inking pad to be absorbedinto the pores of the cover, and thus prevent the dripping of the inkfrom the duplicating apparatus. The absorbed ink vehicle does not becomeseparated from the ink pigment within the cover and does not evaporatefrom the ink.

Various features of the above described inking pad and cover will beperceived from the following examples.

4. Example 1 A one percent solution of a chromium complex of aperfluoroacid, commercially available as Minnesota Mining Scotch Guard803, in methyl alcohol is prepared and an inking cover constructed fromsulphite paper and an inking pad of a cotton flannel having a nap on oneside is immersed in the perfiuoroacid solution for three minutes, a timefound sufiicient for the cover and inking pad to become thoroughlywetted by the solution. The cover and inking pad are removed from thesolution, the excess solution is removed from the cover and pad bywringing, and the cover and pad are air dried.

A cover and inking pad are produced which greatly diminish the capillaryseparation of the ink vehicle from the ink pigment in both water baseand oil base inks and repeated use of the cover and inking pad producedshows that the ink Within the perforated drum does not evaporate throughthe surface of the inking pad or become crusted upon the inking pad orthe interior of the perforated drum.

Example 2 An inking pad and cover were made according to the method ofExample 1 employing a five percent solution of a silicone resin, onesuch resin commercially available being Dow Corning Antifoam A. Thecoated inking pad and cover were found to resist the capillaryseparation of water based inks and likewise allowed the opera tion of ofa duplicating apparatus for extended periods of time with long offcycles with a significant reduction in the evaporation of the vehicle orcaking of the ink pigments either on the inking pad or within theperforated cylinder.

Example 3 An inking pad and cover are made from a cotton flannel clothand sulphite paper respectively by immersing the inking pad and cover ina five percent water solution of sodium stearate until thoroughlyWetted. The inking pad and cover are then treated with a five percentsolution of calcium chloride which reacts with the sodium stearate toproduce insoluble calcium stearate and the inking pad and cover aredried. After drying the inking pad and cover are subjected to a heattreatment to melt and fuse the calcium stearate onto the surface of theindividual fibers of the inking pad and cover. The inking pad and coverproduced are ink repellent to water base inks and diminish the capillaryseparation of the ink vehicle from the ink pigment.

Example 4 An inking pad and cover were made according to the method ofExample 1 employing a five percent solution of chromium complex ofstearic acid, commercially available as Du Pont Quilon. The ink pad andcover produced are of a nature which reduced the capillary separation ofwater base ink vehicle and likewise allowed the repeated operation ofthe duplicating apparatus Without the degradation of the ink.

Example 5 An inking pad and cover are constructed fromtetrafiuoroethylene ink repellent fibers. The inking pad and coverexhibits similar ink repellent properties as the ink repellent coatedinking pad and cover of Example 1 and resists the capillary separationof the ink vehicle of both water base and oil base inks.

A method employed to determine the precise amount and level of treatmentof the inking pad and cover fibers in order to provide an inking pad orcover which will not support the capillary separation of the ink vehiclefrom the ink pigment is one which employs the measurement of the angleof contact of the ink vehicle on the surface of the inking pad or coverwhich has been treated in a manner as set forth in the precedingexamples. The angle of contact is the internal angle (i.e. within thedroplet) formed by a plane tangent to the droplet at the point where itcontacts the surface of the inking pad or cover. An angle of more than90 degrees occurs when the droplet of ink vehicle forms more than ahemisphere on the surface of the inking pad or cover. A drop of the inkvehicle is placed on the surface of the inking pad or cover and theangle that the droplet of ink vehicle forms with the inking pad or coveris measured after equilibrium has been reached. It has been found thatan angle of contact of more than 90 degrees is necessary to prevent thecapillary separation of the ink vehicle from the ink pigment within theinking pad or cover. If the droplet of ink vehicle assumes an angle ofcontact of 90 degrees or less the inking pad or cover will besusceptible to the capillary separation of the ink vehicle from the inkpigment and will not be suitable to overcome the disadvantages attendanttherewith.

Although the inking pad and cover have been particularly described withrespect to their use in a duplicating apparatus of the rotatable drumtype it is apparent that the ink repellent inking pad and cover can alsobe utilized in other forms of duplicating apparatus, such as the belttype stencil duplicating machines or conventional inking duplicatingdevices, (eg stamp pads and the like) where evaporation and thecapillary separation of the ink vehicle from the ink pigment isundesirable.

It can be seen that an inking pad and cover have been provided whichgreatly diminishes or prevents the capillary separation of the inkvehicle from the ink pigment. By preventing the separation of the inkvehicle from the ink pigment, conventionally available duplicatingapparatus can be operated with repeated on and oif cycles without thenecessity of a rigorous maintenance of the machine or the frequentcleaning or replacement of the inking pad and cover and/ or printingink.

Various of the features of the invention are set forth in the followingclaims.

What is claimed is:

1. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web material having interstices formed between adjacentfibers for passage of ink therethrough, means for attaching said inkingpad to a duplicating apparatus, said fibers being ink repellent to adegree sufficient to substantially restrict the flow of ink through saidinterstices by capillary action, said interstices being of a size suchthat said inking pad has a sufiicient porosity to allow the flow of inktherethrough under printing pressure.

2. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web material having interstices formed between adjacentfibers for passage of ink therethrough, means for attaching said inkingpad to a duplicating apparatus, said fibers being ink repellent to adegree sufiicient to form an angle of contact of more than 90 with adroplet of ink vehicle whereby the flow of ink through said intersticesby capillary action is substantially restricted, said interstices beingof a size such that said inking pad has a sufiicient porosity to allowthe flow of ink therethrough under printing pressure.

3. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web formed from an ink repellent material, said inkingpad having interstices formed between adjacent fibers for passage of inkthere through, means for attaching said inking pad to a duplicatingapparatus, said fibers being ink repellent to a degree sufficient tosubstantially restrict the flow of ink through said interstices bycapillary action, said interstices being of a size such that said inkingpad has a sufiicient porosity to allow the flow of ink therethroughunder printing pressure.

4. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web formed from an in repellent material selected fromthe group consisting of fluorocarbon resins and polyolefin resins, saidinking pad having interstices formed between adjacent fibers for passage=of ink the-rethrough, means for attaching said inking pad to aduplicating apparatus, said fibers being ink repellent to a degreesuflioi-ent to substantially restrict the flow of ink through saidinterstice by capillary action, said interstices being of a size suchthat said inking pad has a sufficient porosity to allow the flow of inktherethrough under printing pressure.

5. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web material having interstices formed between adjacentfibers for passage of ink therethrough, means for attaching said inkingpad to a duplicating apparatus, said fibers having an amount of an inkrepellent coating material thereon sufiicient to substantially restrictthe flow of ink through said interstices by capillary action, saidinterstices being of a size such that said inking pad has a sufiicientporosity to allow the flow of ink therethrough under printing pressure.

6. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web material having interstices formed between adjacentfibers for passage of ink therethrough, means for attaching said inkingpad to a duplicating apparatus, said fibers having an. amount of an inkrepellent coating material thereon sutli-cient to substantially restrictthe flow of ink through said interstices by capillary action, saidcoating material being selected from the group consisting of chromiumcomplexes of periiuoroacids, fluorocarbon resins, silicone resins,waxes, insoluble salts of fatty acids having at least about 12 carbonatoms, and chromium complexes of fatty acids having at least about 12carbon atoms, said interstices being of a size such that said inking padhas a sufficient porosity to allow the flow of ink therethrough underprinting pressure.

7. An inking pad for use with a duplicating apparatus comprising, aporous fiberous web material having interstices formed between adjacentfibers for passage of ink therethrough, means for attaching said inkingpad to a duplicating apparatus, said fibers having a coating of betweenabout 0.1 percent and about 25 percent by weight of an ink re ellentcoating material selected from the group consisting of chromiumcomplexes of perfiuoroacids, fluorocarbon resins, silicone resins,waxes, insoluble salts of fatty acids having at least about 12 carbonatoms, and chromium complexes of fatty acids having at least about 12carbon atoms, said coating restricting the flow of ink through saidinterstices by capillary action, said interstices being of a size suchthat said inking pad has a sufii oient porosity to allow the flow of inktherethrough under printing pressure.

8. For use in a duplicating apparatus, a cover for covering an inkingpad comprising, a porous fiberous web material having interstices formedbetween adjacent fibers for passage of ink therethrough, means forattaching said cover to a duplicating apparatus, said fibers being inkrepellent to a degree sufficient to substantially restrict the fiow ofink through said interstices by capillary action, said interstices beingof a size such that said cover has a suilicient porosity to allow theflow of ink therein under pressure.

9. For use in a duplicating apparatus, a cover for covering an inkingpad comprising, a porous fiberous web material having interstices formedbetween adjacent fibers for passage of ink there'through, means forattaching said cover to a duplicating apparatus, said fibers having anamount of an ink repellent coating material thereon suf ficient tosubstantially restrict the flow of ink through said interstices bycapillary action, said coating material being selected from the groupconsisting of chromium complexes of perfluoroacids, fluorocarbon resins,silicone resins, waxes, insoluble salts of fatty acids having at leastabout 12 carbon atoms, and chromium complexes of fatty 7 8 acids havingat least about 12 carbon atoms, said inter- 2,651,255 9/ 1953 Wallich101125 stices being of a size such that said cover has .a suflicient2,662,835 12/ 1953 Reid 117-135.5 porosity to allow the flow of inktherein under pressure. 12,303,615 8/1957 Ahlbrecht t a1. 117135.52,323,144 2/1958 Dalton 117-1355 X References Cited by the Examiner 52,895,853 7/1959 Snyder et a1. 117-4355 X a 3,002,449 10/1961 Sherman101-1 19 2096 753 ii f f I 117 135 5 3,089,806 5/1963 Mizell 117135.5 X

urp ye a. 2 173 243 9 1939 Young 7 135 EUGENE CAPOZIO, Exammer-2,510,838 6/1950 Sherman 101--125 X 10 ROBERT E. PULFREY, Examiner.

1. AN INKING PAD FOR USE WITH A DUPLICATING APPARATUS COMPRISING, APOROUS FIBEROUS WEB MATERIAL HAVING INTERSTICES FORMED BETWEEN ADJACENTFIBERS FOR PASSAGE OF INK THERETHROUGH, MEANS FOR ATTACHING SAID INKINGPAD TO A DUPLICATING APPARATUS, SAID FIBERS BEING INK REPELLENT TO ADEGREE SUFFICIENT TO SUBSTANTIALLY RESTRICT THE FLOW OF INK THROUGH SAIDINTERSTICES BY CAPILLARY ACTION, SAID INTERSTICES BEING OF A SIZE SUCHTHAT SAID INKING PAD HAS A SUFFICIENT POROSITY TO ALLOW THE FLOW OF INKTHERETHROUGH UNDER PRINTING PRESSURE.